Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, medical devices, automobiles, portable electronic devices and other applications. The technology used to manufacture image sensors, and in particular CMOS image sensor (“CIS”), has continued to advance at a great pace. Modern image sensor applications place demands for faster processing speeds and better image quality, while simultaneously expecting miniaturization in the physical size of the image sensor.
Some electronic devices, as such cell phones and cameras, include multiple image sensors to perform different functions, such as, capturing images and monitoring ambient light levels for measuring the luminance of an environment. In some cases, a single image sensor may include two separate and distinct arrays of pixel cells, one dedicated for the sole purpose of image acquisition and the other dedicated for the sole purpose of ambient light detection. These standalone devices or single purpose pixel cell arrays increase the complexity, expense, and power consumption of consumer electronics that include both an image sensor array for image capture and an image sensor array for ambient light detection.